1. Field of the Invention
The present invention relates to a removal tool, more particularly, to a removal tool for a damaged fastener.
2. Description of the Prior Art
In many devices or mechanisms, plenty of fasteners (such as bolt, screw, nut, a threaded insert or the like) are used to connect parts. The fastener is usually driven by a tool such as wrench which is engaged with a head portion or a receiving hole of the fastener, and the wrench is then rotated to fasten or unfasten the fastener. However, many factors, such as that the fastener is fastened or unfastened for many times, that an improperly great force is applied to the fastener, or the properties of material of the fastener, can cause damage to the head portion or the receiving hole so that the fastener cannot be removed.
U.S. Pat. No. 6,575,057 is directed to a broken heater hose coupler removal tool. One end of the removal tool is adapted for being connected to and driven by a drive device, and the other end is formed with plural teeth which symmetrically extend and are parallel to a longitudinal center axis, namely, the teeth are untwisted. The teeth section includes an end section and a mid section. The end section and the mid section include respective fixed radial cross section areas, and the radial cross section area of the end section is smaller that of the mid section. The end section is inserted into the broken heater hose coupler in advance, the broken heater hose coupler is then removed through the engagement of the apexes of the teeth with the coupler. However, since the teeth are straight and parallel to the longitudinal center axis, and since the end section and the mid section include the respective fixed radial cross section areas, so that the removal tool has to be hammered to fit the teeth into the damaged coupler when the damaged coupler is to be removed. Therefore, the removal process is complicated and inconvenient, and the teeth cannot be wedged further into the damaged coupler when the removal tool is rotated, so that the removal tool can slip and rotate relative to the damaged coupler and the damaged coupler might be hard to be removed.
U.S. Pat. No. 1,875,484 is directed to a screw extractor. A plurality of ribs straightly extend along a longitudinal direction of the screw extractor on the circumferential surface. The screw is removed through the ribs being wedged into the screw. However, the straightly-extending ribs cannot be sufficiently and effectively wedged into the screw when the screw extractor is rotated, so that the screw extractor might slip and rotate relative to the screw and the screw might be hard to be removed.
TW I337116 is directed to damaged bolt and screw removing devices. The removing device includes a tip from which extend two or more notches separated by traction or biting surfaces formed from two-sided frusto-conically-shaped regions. The surfaces are bounded on one side by a nonlinear cutting edge and on the other side by a non-cutting edge and are configured to cut into the fastener when the bit is rotated in a direction opposite to the fastener's direction of engagement. Specific embodiments include configurations where the cutting edges extend at different angles with respect to the bit axis, where the biting surfaces comprise a plurality of serrations, and where the cutting edges are separated by flutes which spiral along a longitudinally extending periphery of the bit. However, since the serrations do not obliquely extend and twist relative to the longitudinal center axis, the serrations cannot be wedged further into the damaged bolt or screw when the removing device is rotated, so that the removing device can slip and rotate relative to the damaged bolt or screw and the damaged bolt or screw might be hard to be removed.
The present invention is, therefore, arisen to obviate or at least mitigate the above mentioned disadvantages.